Central compressor variable refrigerant flow air conditioning sysytem

ABSTRACT

An oil-free central compressor variable refrigerant flow air conditioning system structure and method is set out. The system may be a new installation, or retrofit. Refrigerant piping spans are not limited by considerations of entrained oil flow.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an apparatus and method for providing refrigerant flow to a plurality of remote evaporators utilizing a single or centralized compressor station and a centralized condenser or condenser station.

2. Description Of The Related Art

In the past, various systems have been proposed for arranging an air conditioning system having a centralized compressor and/or centralized condenser station.

However, all prior art proposals were severely curtailed in their application, due primarily to a refrigerant piping length limitation related to the inherent characteristics of conventional compressor technology.

Prior art refrigerant piping lengths were limited by the particular systems ability to maintain proper oil return, due to the necessary entrainment of lubricating oil present in conventional refrigerant lines to enable operation of conventional compressors.

The absolute maximum length of refrigerant lines has previously been limited to approximately 500 feet, but actually is often limited to approximately 135 feet from the first “tee” from the condensing unit to the furthest evaporator element.

Generally, in the past the following guidelines applied to the maximum allowable refrigerant piping lengths:

-   -   maximum allowable vertical distance between outdoor condenser         and indoor evaporator is 165 feet.     -   maximum permissible vertical distance between two individual         indoor evaporator units is 50 feet.     -   maximum overall refrigerant piping length, between the outdoor         elements and the furthest indoor unit is 540 feet.

Prior art systems required an oil retrieval mode, for example where the expansion valves open and the compressor cycles at high pressure to flush oil out of piping areas where it has accumulated.

Also, each compressor would require its own oil separators which would be optimized to the system.

A need exists to overcome the inherent drawback of prior art systems.

BRIEF SUMMARY OF THE INVENTION

In view of the aforementioned drawbacks in certain prior art chiller heater systems, a new system is proposed which allows virtually unlimited distances between the compressor units and the evaporator heat exchangers.

It is an object of the invention to set out a central compressor air conditioning system which has no inherent limitations in the refrigerant piping distance between the central compressor and the various evaporator elements.

Specifically, it is an object of the invention to set out a central compressor air conditioning system having no entrained oil in the refrigerant lines.

More particularly it is an object of the invention to set out a central compressor air conditioning system having a magnetic levitation bearing compressor which requires no entrained oil in the refrigerant fluid.

It is another object of the invention to provide an apparatus and method for retrofitting conventional multi-compressor air conditioning systems with a centralized compressor station/condenser station arrangement.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic drawing of one embodiment of the system.

FIG. 2 is a schematic drawing of a retrofit application of the present invention.

FIG. 3 is a schematic drawing of a retrofit application of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 sets out an overall schematic view of the present application. Central station compressor 1 consists of magnetic levitation bearing types requiring no entrained oil in the refrigerant fluid. It compresses the oil free refrigerant and delivers it to a central condenser package 2 for removal of heat from the refrigerant. Thereafter the refrigerant travels to the various evaporators 3 which are placed in the building space at locations where heat is to be removed from the space.

Expansion valves 4 are disposed at appropriate locations upstream of the various evaporators 3.

By controlling the refrigerant flow to each evaporator 3, using an electronic control/flow control system (not shown), the amount of cooling can be carefully and specifically regulated at each cooling location.

By virtue of the present invention, the distances in the spans of the refrigerant piping are no longer limited in particular due to the absence of entrained oil in the refrigerant lines. Spans of well over 500 feet are for the first time possible.

FIG. 2 sets out one embodiment of a retrofit application. Here, a central retrofit magnetic/levitation bearing compressor 10 station delivers oil-free refrigerant to a central retrofit condenser station 20. Old pre-existing compressors 50 and condensers 40 are taken out of service, and condensed refrigerant is delivered directly from the retrofit compressor/condenser station to the individual evaporators.

An electronic control/flow control system (not shown) may be installed to control the refrigerant delivered to each individual evaporator unit 30.

Expansion valves 60 and 70 and other valves not shown may be controllable to assist in the control of refrigerant delivered to each evaporator.

FIG. 3 sets out another embodiment of a retrofit application. Here, a central retrofit magnetic levitation bearing compressor 11 delivers oil-free refrigerant to old existing condensers 13. Old existing compressors 12 are taken out of service. Oil-free refrigerant is delivered through expansion valves 14 to existing evaporators 15.

For the first time, new installations and retrofit installations can utilize the benefits of centralized compressor and/or condenser stations without being limited by the refrigerant pipe length limitations of the prior art systems.

Many advantages are presented including; more efficient utilization of compressor electrical energy, closer control of cooling output by control of refrigerant flow, avoidance of multiple compressor installations, less intrusive piping structures, reduction of costs, and reduction of greenhouse gas production. 

1 . A central compressor station multipoint vapor compression air-conditioning system, comprising: a physically centralized compressor station having at least one magnetic levitation bearing type compressor requiring no entrained oil in refrigerant fluid compressed by said compressor, a physically centralized condenser package for removal of heat from said refrigerant fluid, a refrigerant fluid piping system having a refrigerated fluid piping system, At least one space to be conditioned, At least one expansion valve located upstream of said evaporators, at least one said evaporator located over 500 feet from said compressor, Wherein refrigerated fluid is delivered from said centralized condenser to said evaporator.
 2. A retrofitted central compressor station multipoint vapor compression air-conditioning system, comprising: Hey physically centralized compressor station having at least one magnetic levitation bearing type compressor requiring no Entrained oil in refrigerant fluid compressed by said compressor, a physically centralized condenser package for removal of heat from said refrigerant fluid, a refrigerant fluid piping system having a refrigerated fluid piping system, At least one space to be conditioned, said space being previously serviced by a separate dedicated compressor and dedicated condenser, so I dedicated compressor and condenser and being disconnected from said fluid piping system, At least one evaporator serving said space, At least one expansion valve located upstream Of said evaporator, At least one I′ve said evaporators located at least 500 feet from said compressor, Wherein the refrigerated fluid is delivered from said centralized condenser to said evaporator.
 3. Hey retrofitted central compressor station multipoint vapor compression air-conditioning system, comprising: Hey physically centralized compressor station having at least one magnetic levitation bearing type compressor requiring no Entrained oil in refrigerant fluid compressed by said compressor, Hey refrigerant fluid piping system Having a refrigerated fluid piping system, At least one space to be conditioned, subspace being previously served by a separate dedicated compressor and dedicated condenser, Said dedicated compressor being disconnected from said piping system, At least one evaporator serving said space, at least one expansion valve located upstream Of said evaporator, At least one of said evaporators being located at least 500 feet from said compressor, Wherein refrigerant fluid is delivered from said centralized compressor to said condenser. 